"My Mister," which centers on a young, gloomy girl struggling to support her poverty-stricken family, and a middle-aged man at her workplace, earned a score of 272.4 on the Content Power Index (CPI) for March 19-25.

The drama had a bumpy ride in the run-up to its March 21 premiere. It had to urgently change one actor, Oh Dal-su, who faced sexual assault allegations. Some TV viewers took issue with the title that they interpreted as alluding to an improper relationship between a young woman and a middle-aged, married man. After all, it cast the 22-year-old singer-actress and 43-year-old actor Lee Sun-kyun.

But the story has been developing differently than previously expected.

Lee Ji-an, played by IU, does whatever it takes to repay her debt to the ruthless loan shark Lee Kwang-il, a son of the cruel moneylender she accidentally killed when she was a middle-schooler. While she tries to use Park Dong-hoon, played by Lee Sun-kyun, in her desperate attempt to earn money, she becomes sympathetic to Park, who suffers the heavy weight of life in his own way.

Although viewership ratings hover below four percent, IU's powerful performance of the sad woman is seen as gripping or even mesmerizing as it is out of sync with her public image of a youthful, buoyant little sister.

The index, created by CJ E&M and Nielsen Korea, measures the level of popularity, trending on social media sites and influence on consumer behavior of entertainment TV programs aired on three major terrestrial networks -- MBC, SBS and KBS -- and seven cable channels owned by CJ E&M, including tvN, Mnet and OCN, during prime time. JTBC, another cable network that airs some highly popular entertainment shows and dramas, is not included in the survey.